I have a system going through any airport security except for TSA where I have precheck.
I have all my toiletries and electronics ready to unload. I put them in the same way in the bins where it is efficient and the x-ray operator can see everything. The gents barking orders at people don't at me. In fact, the last time, earlier this month, the security person watching just nodded his head.
For some reason, they usually find something they want to double check but that is quick as they pinpoint exactly what it is. This last time, I had extra stuff and thought I would definitely get stopped but I wasn't.
It could also be that I am usually in the Fast Track lane but I don't know if that makes a difference.
Tips for Heathrow and much of the UK:
1) Toiletries must be in regular zip loc bags. The airport has them for free. (Nice ones, too, with a handle.) You can then put that zip bag in a different 3-1-1 case but it must be in the zip loc.
2) All electronics must come out that are larger than an ereader. Lay them flat. Not on top of each other.
3) Belts off but shoes can stay on--unless they are thick or heavy boots.
4) Make sure everything is out of your pockets.
5) Bags in separate bins. Carry-on in one. Personal Item, jacket and belt in another. They seem to like a third bin for electronics and toiletries.
By doing the above, I never get hassled. I may get pulled aside because they see something they don't like, but never rude. Some of the items they've dinged were a travel size roll of duct tape, solid deodorant, 0.5 oz bottle of hand sanitizer (in the 3-1-1 bag) and a shaving stick.
I hope this helps some of you.